Investigation of the human glomerulus in health and disease shows that the human glomerulus comprises seven lobule-like structures with numerous anastomoses. The total length of the capillaries in a single glomerulus is 0.95 cm, making a total of 19 km for all 2-million glomeruli. The total surface area of all glomerular capillaries is 6,000 cm2. The total filtration surface area is 516.1 cm2. Severe isolated disease of the glomerulus, as seen in acute endocapillary glomerulonephritis, membranoproliferative glomerulonephritis types I and II, membranoproliferative glomerulonephritis plus chronic membranous glomerulonephritis, diabetic glomerulosclerosis, and glomerular amyloidosis, does not lead to elevation of serum creatinine concentration, even if the filtration area is reduced to about 20% (as in diabetes) of the normal value. It is concluded that isolated glomerular disease does not lead to elevation of the serum creatinine concentration. Glomerulopathies in which there is acute or chronic elevation of the serum creatinine concentration are accompanied by acute renal failure or involvement of the renal cortical interstitium, respectively.